Patterns of allozymic variation within Calluna vulgaris populations at seed bank and adult stages

We investigated the spatial genetic structure within and between two plots of Calluna vulgaris and the extent to which the soil seed bank differed gen etically from adults at seven allozyme loci. Averaged over the two plots, t he seed bank and adult populations contained very similar levels of genetic diversity. Moreover, seeds contained in a single soil core (100 cm(3)) exh ibited similar mean allozyme diversity to the surrounding adult population, indicating that the seed bank preserves genetic diversity at a very local scale. Few differences in allelic frequencies were found between the seed b ank and its surrounding adult population in each plot. Mean G(ST) indicated a lack of differentiation between the two plots at adult (G(ST) = 0.008) a nd seed bank (G(ST) = 0.002) stages. Low interplot differentiation is consi stent with the outcrossing mating system of the population (t(m) = 0.91 in one plot) and its history of human disturbance. In contrast, spatial autoco rrelation analysis of adults indicated a genetic structure at a very local scale, with positive autocorrelation for all alleles below 2 m in one plot and with a pattern of positive autocorrelation below 8 m in the two plots. Current limitation to seed dispersal rather than spatial extension of clone s is thought to be responsible for local genetic structure.